Spark plug shield



March 21,1939. E.N JACOBI 2,151, 112

SPARK PLUG SHI ELD Filed Jan. 8, 1937 q B MZ/ EUWETUN. Jmbz M Patented 21, 1939 UNITED STAT-Es PATIENT OFFICE,

SPARK PLUG SHIELD Edward N. Jacobi, Milwaukee,

Wis.,' assignor to Briggs &' Stratton Corporation, Milwaukee, Wis., a corporation of Delaware Application January 8, 1937, Serial No. 119,543

and interference with radio reception, and in.

view of the wide use of radio receivers in automolo biles and in locations where stationary internal combustion engines are in operation, it is not only desirable but essential to prevent the radia- -tion of such energy.

Shields have been used for this purpose before, as shown in Patent No. 1,806,548 issued to Hector Rabezzana, but the shields heretofore in use have been comparatively costly and not'readily applied to spark-plugs in position on an ensine.

- Itis therefore an object of this invention to simplify and improve the construction of such shields with a view toward decreasing their cost of manufacture and facilitating their application to the spark plugs.

Another object of this invention is to provide a shield of the character described which is formed in complementary sections and in which the juncture between the sections, is so formed as to insure against leakage of electrical energy therethrough.

With a view toward affording ready access to the spark plug, it is a further object of this invention to provide a shield of the character described'wherein the line of part between the complementary sections is on a: horizontal plane normal to the axis of the plug so that when the top section is removed, the upper plug is iree and unobstructed.

With/the above and other objects in view which 40 will appear as the description proceeds, this invention resides in the novel construction, combination and arrangement of parts substantially as hereinafter described and more particularly defined by the appended claims, it being understood thatsuch changes in the precise embodi-- ment of the hereindisclosed invention may be made as comewithinthe scope of the claims.

The accompanying drawing illustrates two complete-examples of the physical embodiment m of the invention constructed according to the best modes so iar'devised tor the practical application of the principles thereof, andin w'hichz' Figure -1 is a side, view showing a shield con- 7 structed in accordance with this invention ap-.

u plied to a conventional spark plug and its lead;

portion of the or notches I6 is suchas to {Claims (01. 123-169) Figure 2. is an end view thereof;

Figure 3 is a perspective view of the two complementary sections comprising the shield shown separated; and

Figure 4 is a view similar to Figure 1, bill, illustrating a-slightly modified embodiment of the invention.

Referring now particularly to the accompanying drawing in which like numerals indicate like parts throughout the several views, the numeral 5 designates a spark plug of conventional design having a metal base 6 at its'lower endby which the'plug is secured in its port, and an upper porcelain end portion 1, the upper extremity of which carries a, terminal 8 for the attachment of a lead wire 9. The medialv portion of the plug has the conventional hexagonal nut formation l0.

The shield, designated generally by the numeral II, is applied over the upper end portion of the plug with its lower end resting on the nut l and completely encloses the upper nonmetallic part of the plug as well as the adjacent end portion of the conductor 9, which is'the only part thereof not covered by a metallic shielding sheath l2.

The shield II is composed of two complementary upper and lower sections l3 and i4. These sections are identical in size and shape so that they may be formed with a single mold. The only difierence between the sections is the provision of a hole IS in the bottom wall of the lower section through which the upper end of the plug passes. The diameter of the hole I is suchthat the bottom wall of the lower section rests on top" of the nut portion l0 grounded thereto. The depth at one end of the closed casing formed by the two complementary sections when in position onthe plug is sufficient to dispose the top wall of the'uppersection a substantial distance above the top of the plug, while theopposite end of the casing. through which the conductor enters is taperingly reduced, as illustrated. At this end of the casing, the meeting marginal edge portions of the two sections have recesses or notches l6 toaccommodate the conductor wire.

so as to be electrically .The size of the hole formed by the recesses grip-the shielding sheath I! when the sections are properly engaged.

Inasmuch as variance in the diameter of the tions and as leakage spaces are to be avoided, flanges are provided atthe meeting marginal edges to provide an overlapping joint. To this end each section has two marginal flanges i1 and II at substantially diametrically opposite portions. The peripheral length of the flanges is slightly less than the corresponding unflanged portions of the marginal edges, so that when the sections are engaged, their interfltting flanges produce a flange extending substantially entirely about the marginal edges of the sections. Consequently, even though the sections may separate slightly, objectionable leakage spaces are entirely avoided. 4

To hold the sections flrmly connected to each other, a screw it is provided. The screw l8 throu h 8 lug 2. on the upper section, and isthreaded intoa tappedhole in asimilar lug 2| on the lower'section.

In this manner the casing sections are securely held together entirely independent oi other (astening means.

As is noted hereinbeiore, the casing is seated.

on the topo! the nut portion ill of the plug and to flrmly hold the same in place thereon a harness spring 22 anchored at its ends to the plug extends over the top of thecasing.

'Ihe specific means for anchoring the ends of the harness spring is, of course, susceptible to substantial modification. I practical manner of anchoring the spring is 11- lustrated in Figures 1 and 2. As here shown, a substantially U-shaped yoke 23 embraces the metal portion 01' the v,plug directly beneath its nut portion II with the outer ends of its arms 24 bent upwardly and extending into substantial alignment with the sides of the casing. Eats 25 bent up from the yoke engage the surfaces of the nut portion lllto hold the yoke against turning.

The extremities of the harness spring are connected to the apertured arms 24, as shown and to hold the upper portion of the spring against displacement lugs 26 are formed on the casing sections asshown, and the flanges it are preferably cut away as at 21 to accommodate the spring and co-act with the lugs 28 in maintaining the spring in proper position.

As noted hereinbeiore, the casing sectionsare securely held assembled entirely independently oi the means for holding the shield in place on the plug, but if desired, the screw I! may be eliminated and the spring 22 relied upon to hold the casing sections bled.

'l'hisconstructionisillustratedinl 'lgure l. The embodiment of the invention here illustrated also utilizes a slightly diilerent manner of anchoring theends oi the spring to the plug, a formed wire member 28 being provided in lieu of the yoke 28.

In all other respects, except the specific shape of the caslngsectlons, the construction illustratedinl lgure iisthe sameasthatshownin Figures 1 to 3, inclusive, attention being particularly'directed to the fact that the edges oi the sections are. also equipped with interfltting flanges to guard against leakage One convenient and' From the foregoing description taken in connection with the accompanying drawing, it will be readily apparent to those skilled in the pertinent art, that this invention provides a spark plug shield which is admirably suited to the purpose for which it is intended and that it is extremely simple, both from the standpoint or manufacture and also its application to the plug.

What I claim as my invention is:

1. A shield to prevent the radiation of electfical energ'yfrom a spark plug which comprises: a casing formed 01 complementary sections identical in shape and construction with the explug for holding the casing in place on the plug.

2. Aspark plug shield comprising: two complementary sections alike as to size and shape so as to permit both to be made with one mold, one of said sections having a holein its wall opposite the open face of the section for the reception of a spark plug, andthe meeting edges of the section being cut away to accommodate a lead wire running to the spark plug; flanges on the meeting edge 01' each section to engage over unflanged portions on the other section; and means for holding the sections assembled.

3. A spark plug shield comprising: two complementary sections engaged at their marginal edges to form a closed casing,one of said sections having a hole to receive a spark plug, said hole being in a wall opposite the open face of the section so that with the casing in place on a spark plug, its line of part is on a plane sub--. stantially normal to the spark plug axis, said sections being alike in size and shape; diagonally opposite flanges on the marginal edge of each section, said flanges having substantially the same length as the unflanged portions of the marginal edges so that the flanges of one section lit over the unflanged edge portions of the other section to provide an overlapping joint extending substantially about the entire casing; and means for holding the sections assembled.

4. A shield for preventing .the radiation of electrical energy from a spark plug which comprises: two complementary similar sections hav ing their marginal edges abutting each other to form a housing and positively limit theirmov'ement together, one of said sections having a hole for the reception of part of a spark plug dis posed in the housing; flanges extending from the marginal edges of each section adapted to overlap unflanged marginal edge portions of the other section for forming a completely overlapped joint between the sections; and means for holding the sections assembled.

EDWARD N. JACOBI. 

